Restore the previously disabled check for regression #3070 on all
compilers but MSVC.
To summarize the issue:
Given namespace fs = std::filesystem.
On MSVC attempting to construct an fs::path from json results in an
ambiguous overload resolution because fs::path can be constructed from
both a std::string as well as another fs::path.
To the best of my knowledge there is no way to fix an ambiguous overload
situation involving a type we do not control and with json implicitly
converting to both std::string and fs::path.
Re-enabling the check where it compiles and keeping it disabled for MSVC
is the best we can do.
Closes#3377 and #3382.
c2054b96b9